A. Field of the Invention
The present invention relates generally to the communications field, and, more particularly to an apparatus for managing and measuring fiber optic cables, and a method for managing and measuring fiber optic cables using the same.
B. Description of the Related Art
Along with the increasing prominence of the Internet has come the wide-ranging demand for increased communications capabilities, including more channels and greater bandwidth per channel. Optical media, such as fiber optic cables, promise an economical alternative to electrical conductors for high-bandwidth long-distance communications. As described in U.S. Pat. No. 6,079,297, assigned to the assignee of the present application, CIENA Corporation, a typical fiber optic cable consists of a silica glass core region that provides a path for optical signals traveling along the cable. The core region is surrounded by a cladding region whose refractive index may be altered to achieve a desired propagation path of the optical signals traveling along the core region. The cladding region is in turn surrounded by an outer protective coating to protect the core region and the cladding region from damage, such as nicks, scratches or dents, which could degrade the long term quality and performance of the fiber optic cable. A fiber optic cable is also protected by a buffer layer that is typically a firm polymer which provides increased protection to the fiber while also increasing the fiber bending stiffness. The buffer layer is formed directly around the protective coating and there is usually a significant adhesive force between the buffer layer and the protective coating.
The glass optical fibers of fiber optic cables have very small diameters, which are susceptible to external influences such as mechanical stress and environmental conditions. The index of refraction of the core is higher than the index of refraction of the cladding to promote internal reflection of light propagating down the core.
Furthermore, the glass fibers in such cables are easily damaged when bent too sharply and require a minimum bend radius to operate within required performance specifications. Damaged fiber optic cables may lead to a reduction in the signal transmission quality of the cables. Accordingly, fiber optic cables are evaluated to determine their minimum bend radius. As long as a fiber optic cable is bent at a radius that is equal to or greater than the minimum bend radius, there should be no reduction in the transmission quality of the cable. If a fiber optic cable is bent at a radius below the minimum bend radius determined for such cable, there is a potential for a reduction in signal transmission quality through the bend. The greater a fiber optic cable is bent below its minimum bend radius, the greater the potential for breaking the fiber(s) contained in the cable, and the shorter the life span of the cable.
Certain uses of fiber optic cables require that a portion of the buffer layer be removed from the fiber optic cable. For example, to make a fiber optic coupler, the buffer layers are stripped from portions of at least two fiber optic cables, and the stripped portions are fused (spliced) together in side-by-side relationship and stretched. It is important that the stripped portions of the fiber optic cables do not become weakened during the stripping process since weakened fiber optic cables can fail during subsequent process steps or during handling of the coupler when tensile stress is applied to the exposed glass optical fiber.
A buffer layer of a fiber optic cable may be removed or stripped in a variety of ways. Buffer layers can be mechanically stripped from an optical fiber by placing the fiber within a precision linear stripper as disclosed in U.S. Pat. No. 6,079,297, discussed above, bringing blades of the stripper into contact with opposite sides of the buffer layer, and then moving the tool relative to the axis of the buffer layer. The bare portion of the fiber usually needs to be wiped with a cloth wetted with alcohol or the like to remove smudges and/or particles of buffer layer that have been deposited on the bare portion of optical fiber by the buffer layer removal process. This type of buffer layer removal process has been built into equipment that performs the tasks of the technician, whereby the process may no be longer manual.
Fiber optic cables are prepared prior to splicing to another fiber optic cable, or joining to a terminating device, by cleaving the fiber to obtain a high-quality endface. In order to obtain low optical losses, the endface of the fiber must be substantially flat and without flaws. In addition to endface quality, one parameter of importance is the angle of the endface to the optical axis of the optical fiber. It is desirable that the plane of the endface be normal to the optical axis, with the fracture angle measuring deviation from the normal.
When the fiber optic cables of two optical components are to be joined or spliced, the end portions of the buffer layers of the fiber optic cables need to be removed. The end portions of the fiber optic cables also need to be cleaved to form endfaces. Typically, the endfaces are formed a predetermined distance from the optical components, by measuring the predetermined distance from the optical component. The endfaces of the cables may then be fusion spliced together. As used herein, the term xe2x80x9csplicexe2x80x9d refers to the assembly of a fused joint of fiber optic cables, and, generally, although not necessarily, a reinforcing bar and a protective sheath (also known as a splice protector).
The optical components may then be installed in an optical communications circuit. Typically, the fused fiber optic cables joining the two optical components are routed, bent, and/or stored in the optical communications circuit. The joined fiber optic cables may be wrapped around two storage mandrels, providing straight and bent portions of the joined fiber optic cables. Therefore, the splice joining the two cables is preferably formed at a portion of the cables that is not bent when the spliced cables are routed, bent, or stored in the circuit. That is, the splice is preferably formed at straight portions of the joined fiber optic cables. When the splice of the joined fiber optic cables is located a straight portion, the splice is subjected to less mechanical stresses than would occur if it were formed at a bent portion.
Since there is typically excess fiber optic cable when the two optical components are spliced, the predetermined distance for forming the endfaces of the cables may occur at multiple points along the lengths of the fiber optic cables. This is fortunate since the cleaving and splicing of fiber optic cables is not always successful.
When the cleaving or splicing of fiber optic cables is unsuccessful, additional lengths of the fiber optic cable buffer layer may need to be removed, and predetermined distances from the optical components for the locations of the endfaces must be measured. The new predetermined distances preferably will occur at a portion of the cables that is not bent when they are routed, bent, or stored in the circuit. Currently, the measurement of the predetermined distances is manually performed by measuring, with a ruler, the distance from the optical components to the desired location of the endfaces. This measurement is cumbersome and time consuming.
In addition, multiple optical fibers or optical devices must be connected via splicing to pieces of terminal equipment, such as optical transmitters and optical receivers, to create functioning optical systems. Present day optical fiber splicing operations require numerous steps, including stripping, cleaning, cleaving, aligning, splicing, recoating, and pull-testing. While each of the individual steps can be performed somewhat quickly, the set-up, preparation and transfer time between the steps of the splicing process consumes a significant amount of time. Also, each of the steps is generally performed manually on a different apparatus or piece of manufacturing equipment. In addition, nearly all the set-up and preparation is performed manually, thereby increasing not only the amount of time for the process, but the possibility of human errors as well.
Therefore, during interconnection of multiple optical components, the optical components are typically mounted in a fiber cassette or organizer so that they may be spliced together. Typically, one or more fiber optic cables emanate from each optical component, increasing the complexity of the arrangement of the optical components, which, in turn, increases the need for more splices. The multiple fiber optic cables in this arrangement generate a web of cables that may confuse the operator charged with the task of splicing optical components together. This increases the chance that the operator will incorrectly splice two optical components together. Incorrectly spliced optical components may damage or destroy the optical components, if the error is not corrected. Correction of an incorrect splice costs valuable manufacturing time and resources.
Accordingly, there exists a need in the art for an apparatus that can measure predetermined points on the fiber optic cable that may be used as splice points, and facilitate the handling of fiber optic cables during an optical fiber interconnection process, whether through a fusion process or a connectorization process. Such an apparatus would reduce the amount of manual intervention by an operator during the process steps and thereby increase the quantity and uniformity of the fiber optic cable and optical devices manufactured through the interconnection process.
The present invention the needs of the related art by providing an apparatus that manages the multitude of fiber optic cables emanating from optic components contained in a fiber cassette, and measures predetermined splice points on the stripped portions of the cables. The apparatus of the present invention may be used in a method for managing and measuring fiber optic cables.
In accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises an apparatus for managing and measuring fiber optic cable, comprising: a mounting base for receiving and retaining a fiber cassette capable of holding at least one optical component having at least one fiber optic cable emanating therefrom; a fiber take up mandrel connected to said mounting base and having a circumference that exceeds the minimum bend radius of the fiber optic cable, wherein the fiber optic cable may be wound around the circumference of said fiber take up mandrel for temporary storage thereon; a fiber retainer rail connected to said mounting base and interposed between the fiber cassette and said fiber take up mandrel, said fiber retainer rail guiding the fiber optic cable from the fiber cassette to said fiber take up mandrel; and a marking mandrel spaced from the fiber cassette and having a circumference that exceeds the minimum bend radius of the fiber optic cable, said marking mandrel having a marking groove formed on its periphery so that the fiber optic cable may be marked at a predetermined location.
Further in accordance with the purpose of the invention, as embodied and broadly described herein, the invention comprises a method for managing and measuring a fiber optic cable with an apparatus having a mounting base for receiving and retaining a fiber cassette, a fiber take up mandrel connected to the mounting base and having a circumference that exceeds the minimum bend radius of the fiber optic cable, a fiber retainer rail connected to the mounting base and interposed between the fiber cassette and the fiber take up mandrel, and a marking mandrel spaced from the fiber cassette and having a circumference that exceeds the minimum bend radius of the fiber optic cable, comprising: mounting an optical component having at least one fiber optic cable emanating therefrom in the fiber cassette; wrapping a portion of the fiber optic cable around the marking mandrel; marking a predetermined location of the fiber optic cable using a marking groove formed on the periphery of the marking mandrel; and wrapping the marked fiber optic cable on the fiber take up mandrel for temporary storage thereon.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.